Because he doesn't like killing. He craves the danger but he doesn't like the idea of killing even the dog. That's why he closes his eyes. < also most people just close their eyes when then shoot a gun.
Sam Winchester moves in with John Watson ( Supernatural and Sherlock ) <<Then why isn't the shirt rack on top and the shelves on bottom? John will never reach his sweaters and Sam is bending over to grab a shirt.
SHERLOCK - Sherlock Holmes (Benedict Cumberbatch) & John Watson (Martin Freeman) - “Johnlock" - "He has got very endearing habits. I'd like a pocket Martin, I think he'd make a good pet." -Benedict Cumberbatch on his co-star the adorable Martin Freeman.